docs: Add separate 'doc/requirements.txt' file

Just to help us separate the documentation-focused requirements from
everything else.

Change-Id: I69e9290addd4424fd8360bffcabc118824a24e20
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

doc/requirements.txt

@@ -0,0 +1,4 @@
+sphinx>=1.7.0,<2.0.0;python_version=='2.7' # BSD
+sphinx>=1.7.0;python_version>='3.4' # BSD
+openstackdocstheme>=1.20.0 # Apache-2.0
+os-api-ref>=1.5.0 # Apache-2.0

test-requirements.txt

@@ -11,9 +11,5 @@ oslotest>=3.3.0 # Apache-2.0
 os-testr>=1.0.0 # Apache-2.0
 pylint==1.4.5 # GPLv2
 python-subunit>=1.2.0 # Apache-2.0/BSD
-sphinx>=1.7.0,<2.0.0;python_version=='2.7' # BSD
-sphinx>=1.7.0;python_version>='3.4' # BSD
 testrepository>=0.0.20 # Apache-2.0/BSD
 testtools>=2.3.0 # MIT
-openstackdocstheme>=1.20.0 # Apache-2.0
-os-api-ref>=1.5.0 # Apache-2.0

tox.ini

@@ -30,6 +30,9 @@ commands = {posargs}
 # This environment is called from CI scripts to test and publish
 # the API Ref and Docs to docs.openstack.org.
 whitelist_externals = rm
+deps =
+  {[testenv]deps}
+  -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf doc/build
   sphinx-build -W -b html -d doc/build/doctrees doc/source doc/build/html
@@ -38,6 +41,7 @@ commands =
 # This environment is called from CI scripts to test and publish
 # the API Ref to docs.openstack.org.
 whitelist_externals = rm
+deps = {[testenv:docs]deps}
 commands =
   rm -rf api-ref/build
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
@@ -61,3 +65,4 @@ local-check-factory = ec2api.hacking.checks.factory
 deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/doc/requirements.txt